Die structure for tangent bending of corrugated sheet metal



July l2, 1960 T. o. wELlNDT 2,944,583

DIE.' STRUCTURE FOR TANGENT BENDING OF CORRUGATED SHEET METAL Filed May 6, 1957 3 Sheets-Sheet 1 l BMM@ Aitorrgeys July l2, 1950 T. o. WELINDT 2,944,583

DIE STRUCTURE RoR TANGENT BENDTNG 0E coRRuGATED SHEET METAL 5 Sheets-Sheet 2 Filed May 6, 1957 FIG. 3

d l 'nIlllIlV INVN TOR.

THEODORE O. WELINDT 7*@ ,00E/@1&4

Attorneys July 12, 1960 T. o. WELINDT DIE STRUCTURE FOR TANGENT BENDING OF' CORRUGATED SHEET METAL 3 Sheets-Sheet 3 Filed May 6, y1957 FIG. 7

INVENTOR. THEODORE O. WELINDT Attorneys DIE STRUCTURE FoR TANGENT BENDING F l 'CGRRUGATED SHEET METAL f Theodore 0. Welindt, Kankakee, Ill., assigner to A. 0. Smith Corporation, Milwaukee, `Wis., a corporation of New York i t l ,I it

Filed May 6, 1957, Ser. No. 657,305

8 Claims. (Cl. 153-46) Y l This inventionrelates to a die construction for a tangent of the corrugations to a substantial radius olvcurvatureV without tearing or wrinklingof -Ythef metal.

bending apparatus and more particularly to a die con- I struction to be used for the tangent bending of corrugated sheet metal. u

, In the manufacture of a corrugated sheetr metal heat exchanger shell for a hot air furnace, the lsheet metal is initialA formed with a series of deep corrugations extending the length of the sheet. The corrugated sheet is then bent longitudinally of the corrugations by a tangent bending method to a generally oval shape to form the shell.

In order toiprovide the required heat transfer characteristics for the shell, the corrugations are formed with a depthV substantially equal to, or greater than, the pitch.Y

During bending of deep corrugations of this type, the portion of the corrugations along'the outer radius of curvature Fig. 5;

of the bend is subjected to severe tens-ion stresses and stretching ofthe metal resulting inmanycases in tears or splits, while the portion of the corrugationsalong the inner radius of curvature of the bend is subjected to compressive stresses resulting in many cases inI severe wrinkling of the metal.

The present .invention 1s directed to a die construction Y for use with a tangent bending apparatus 'which substantially eliminates the splits and wrinkling of the deeply corrugated sheet metal which occurs with conventional die structures. s l

According tothe invention, the die construction includesan upper die member haying a generally curved working face formed withfaseries of corrugations which complement the corrugations of the sheet to bebent.

A lower die member is adapted to 'cooperate with the upper die member and is supported for rockingmovement with respect totheY upper die member. The'sheet is clamped between the die membersandk as the lower die member istk `rocked or pivoted with relation tothe upper die member, the sheet is progressively bent'to the curvature of the working face of the Upper diepmember.

As the corrugated sheet to beibent is never absolutely true in dimension and fgener'ally has some camber throughout its length, they inner portion'of the lower die member is planarv and free of corrugationswhile the outer portion is provided with corrugations which'complement the corrugations of theupper die member. WhenY the sheet is clamped between the die members, the portion of the sheet in the area of the hat die surface can adjust itself to thereby insure that the end portion of theV sheet will properly nest within the corrugated'die members; I

In order to provide aY degree of overbending .to compensate -for rebound or spring-back in the bent portion of the metal sheet, the outer end of the corrugated portion of the lower die member .is inclined upwardly at a slight angle to a horizontal plane and the curved Working face if of the upper die is formed to complement inclined section. s The present invention provides a die construction for use withF a tangent bending apparatus which enables `The drawings furnished' herewith mode contemplated ofrcarrying out the invention.

VOther objects and advantages will appear inthe course of" the following description. v

illustrate, the best In the drawingsz. f s Figure 1 isa perspective, View of a tangent bending apparatus incorporating the die construction of .the invent tion; s i

Fig. 2 is a ansverse section of the die assembly with the dies inthe open position; Fig. 3 is a view of the die assembly according to the plane of line 3 2V in Fig. 2 with the dies in the closed position and the metal sheet clampedtherebetween;

` Fig. 4 is an enlarged fragmentary transverse section of the die assembly showing the ilange of the sheet contained within a pocket in the lower die; i i Fig. 5 is a transverse section showing the 'locking' brackets for clamping the upper dies in the closed position;`

Fig. 6` is a .top plan view of the structure shown in Fig. 7fis a fragmentary top plan view with parts broken away'and showing the hydraulic cylinder employed to raise'and lowerthe upper dies;- j v Fig.--.8ris a rear elevation with parts broken away of the structure shown inlFigLr7;

Fig. 9 is a sectional iew similar tol-lig. 2, showingone end ofr the sheet being bent;

- Fig. Y10 isa perspective view of the corrugated metal sheet before bendingrand i Fig. 11V is a side elevation of the completed oval-shaped bent sheet.

The drawlngs illustrate af'conventional tangent bending machine in which a at corrugated sheet or workpiece 1 is bent to. a generally oval configuration.

The sheet 1, as shown in Fig. 10,Y is formed with a series of'deeplongitudinally extending corrugations 2, and each sideledge of the sheet is provided with a' ilange 3 which 'extends the length of the sheet; The sheet 1 is adapted to be bent in a direction longitudinally of the corrugations i'n'iaY series of tangential bending operations to: a generally oval or elliptical shape. The ends ofthe sheet are then secured together to form a heat ex- Vchangershellorthelike. f 'j The tangent bending ma'chinelicomprisesV in general,

a frame 4 whichis mounted vort-a foundation 5 and sup=v ports a pair of lower wing dies 6 and 7,. The-wing dies are rockably mounted with respect to a pair of upper dies 8` and 9- havingvthe curvature ofthe shell to be formed. .The sheet lis adapted to be clamped between the upper and lower dies, andrthe lowerY dies areeach rocked or pivotedrupwardly around the corresponding curved upper diertoprogressively bend the 4sheet 1 to the curvature of theV upperdies. r Y To .supportjtheV lower wing dies 6 and 7,.two pairsof brackets 10 are pivotally connected to Vupstanding side lugs 11 on frame 4by pins 12 at the sides of the frame.

' The bottom surfaceof each pair of brackets 10 is adapted vdeeplycorrugated:sheetmetal to be bent-,in the direction j, l

rto reston a -supportbar 13` which is mounted on `up Y per portion ofi-the frame 4 at the sidesthereof. The brackets-10 arefprovided with horizontal guideways .14, and a .dievv supportA plate 15 is slidably disposed within Vthe Vguideways in each pair of brackets. The die supportplate" 15 inturn supports-.a bolster plate 1.16, and A i vthe lower dies `6 and 7 are bolted orVQthe'r-wise secured "toY "the respective bolster plates.

To rock or pivot the lower dies upwardly aboutithe respective upper dies, the piston rod i a doubleact- .m :ing hydraulic cylinder 18'is pivotally attached to each ofthe brackets 10 and the lower end'of each cylinder 18 ispivotally connectedrto the lower` end portion of Yframe j s :Patented Jun-172, 196e 4. Hydraulic uid is introduced into the cylinders through Ilines 19 from a source, not shown.

By introducing hydraulic fluid into the lower end portion of` cylinders 18, the piston rods 17 are extended, and the die support plates 15 and the lower dies 6 and '7 are thereby pivoted upwardly to a generally vertical position, as shown in Fig. 9, while retraction of the piston rods 17 will pivot the lower dies downwardly to a generally horiz'ontal position.

To guide the die support plates 15 during rocking movement and maintain alignment of the side edges thereof, a rack 20 is securedto each side edge of each plate 15 and is adapted to mesh with a gear segment 21 which is attached to the lugs 11 on frame 4. As the die support plates 15 are rocked with respect to the frame 4, the rack 20 travels on the gear segment 2l and maintains alignment of the plates `15 and the dies 6 and 7.

The upper dies 8 and 9 are adapted to be lowered toward the lower dies andare locked in the lowered position so that the lowerl dies can be pivoted therearound and progressively bend Vthe corrugated sheet 1 disposed between the dies. The upper dies 8 and 9 are carried by armsA 22 and 23, respectively, and the inner end of each arm is connected to a support plate 24 at the Vside of the frame. v The upper dies 8 and 9 are raised and lowered by slidably mounting the support plate 24 on a column 25 which extends upwardly from theside of frame 4. To mount the supportv plate 24 for sliding movement on column 25, the column is provided with a pair of outwardly extending flanges or guides 26 which are slidably disposed within vertical guideways 27 formed in the support plate. The support plate is moved vertically in relation to the column by means of a hydraulic cylinder 28 which is disposed `within the column 25. The upper end of cylinder 28 is secured to upper plate 29 of column 25 and the piston rod 30 of the cylinder is connected'to the lower portion ofthe support plate. Hydraulic uid is introduced into the ends of the cylinder 28 through lines 31 from a source, not shown.

In order tofacilitate unloading of the bent sheet 1, arm 23` and the corresponding upper die 9 are adapted to be moved relative to the other arm 22 'and the corresponding die 8. This is accomplished by securing the inner end ofarm 23 to a bracket 32 which is slidably mounted within horizontal guideways 33 formed in the upper and lower ends of the support plate 24.

The arm 23 and die 9 is moved laterally toward and away from arm 22 and die 8 by a hydraulic cylinder 34. The outer end of cylinder 34 is secured to support plate 2-'4 while the-piston rod 35 of cylinder 34 is attached to bracket 32. Hydraulic fluid is introduced into the ends 'of cylinder 324 through lines 36 from a Asource of fluid under pressure, not shown, to retract and extend rod 35 and thereby move die 9 toward and away from die 8.

After completion of the bending operation, the corrugated sheet 1 has a generally ovalshape and can be `conveniently removed from the raised upper dies by moving arm 23 toward arm 22 to decrease the spacing between the upper dies. With the arms 22 and 23 in closed relation, the oval sheet can be readily slipped from the upper dies 8 and 9 over the free ends of the arms.

' To assure alignment of the upper dies with the lower dies, a pair of Vguide bars 37 are Vsecured to the upper end yoi? frame 4 and are provided with notches 38 which receive arms 22 and 23 as the upper dies are lowered toward the lower dies.

" To lock the upper dies 8 and 9 in the lowermost posil `outer Vends of the respective arms 22 and l23 'when the upper dies are in the lowermost position. y

Ihe locking'arm's 39'ar'e actuated by Vm'e'a'ns of double acting cylinders 43 which are pivotally attached to the lower end of brackets 40. Cylinders 43' carry piston rods 44 which are pivotally attached to the lower end of the t.-shaped locking arms. Hydraulic uid is introduced into the ends of cylinders 43 through lines 45 from a suitable source of uid under pressure. By extending piston rods y44 from the cylinders 43, the locking arms 39 are pivoted inwardly to .bring hooks 41 into engagement with brackets i42 and hold the outer endy of the arms against movement. p

'in addition to locking arms 39, two pairs of inner locking brackets 46 are provided which engage the arms 22 and 23 on either side of the upper dies when the upper dies are in their lowermost position.' The locking brackets 46 are pivotalily connected to guide bars 37, and to this end the guide bars are provided with embossments 47 having slots 48 within which the locking brackets 46 are pivotally secured. The upper end of each bracket 46 is provided with a hook 49 which is adapted to engage the upper surface of the respective arms 22 Vand 23 when the brackets are in locking position.

The locking brackets 46 are connected together by a pairof links 50 which serve to actuate the brackets in unison. The connection of links 50 to brackets-i6 is such that brackets 46 will move in oppositeV directions to simultaneously engage or withdraw from the respective arms 22 and 23.

The brackets are actuated by a hydraulic cylinder 51 and piston rod 52 of the cylinder is connected to a connecting arm 53 which is attached to one ofgthebrackets '46. With this construction, an vextension of the piston rod 5 2 from the cylinder 51 moves the brackets inwardly into engagement with the arms to lock the Vsame against movement. j

Accordingto the invention, the outer end portion of the working face of each lower wing die 6 and 7 is provided with a series of deep corrugations 514 which complement the corrugations 2 of sheet 1, `and the innerend portion of the working face denes aV generally flat surface 55 whichis in substantially the same plane as the bottom or root of the corrugations 54.

To provide a degree of overbending to compensate for spring-back of the bent sheet, the outer portion 'of the corrugations 54 are inclined upwardly at a slight angle to the horizontal, as indicated by 56.

The inner ends of corrugations 54 adjacent 'surface 55 are tapered, as indicated by 57, to prevent tearing of the sheet during clamping. H p

The sheet 1 to be bent is supported on the lower dies 6 `and 7 with the corrugations 2 at the end portion of the Sheet registering with the corrugations 56 of the dies and the corrugations at the longitudinal center portion of the sheet 1 being spaced slightly above flat surface 55.

The side anges 3 of sheet 1 are disposed'falong the sides ofthe die 6 and are contained by the side bar flanges 58 of upper die 8, as'shown in Fig. 3. However, inthe case of die 7, which is intended to bend the sheet 1 to a smaller radius of curvature, the side bar flanges 58 are eliminated and the lower die 7 is provided with side bar flanges 59. The flanges 59 are formed with slots 60 to receive the flanges 3 of the sheet. As shown in Fig. 4, the anges 3 are bottomed within the slots 6i) so that pressure is applied to the flanges during the bending operation to prevent the flanges from crawling out of the slots. Y

7: The upper dies 8 and 9 have working faces formed with a series of corrugations 61 which complement the corrugations 54 in dies 6 and 7 and are adapted to register .with corrugations 54 to clamp the sheet 1 therebetween. The working face Vof each upper die includes a straight portion 62 disposed to cooperate with the at surface 55 0f the corresponding lower die and a curved end portion 63 having the desired curvature ofthe bend to be made vand disposedv to' co'op'eratewith corr'ugations 54 and 56 off the lower die. The working faces Aof Vdies 8 and- 9 Vare r prima The upper extremity of the working faces of dies 8 and V9 are provided with a contour to complement the inclined corrugations 56 of the lower dies.

'Ihe inclined corrugations 56.0f the lower dies andthe cooperating corrugations .of the upper dies, permit overt Inj final bending operation, the previouslybent end' of theu sheet is maintained in aligned with the end being bent in the nal operation by a wiper guide 66 which is secured to the upperY d ie 9.,- Thev previously bent end of the vsheetis adapted to engage the guide 66V as the sheet is bent around die 8. The guide 66 serves to maintain Y alignment of the ends of lthe sheet 1, so that the corrugations 2 at the ends will be properly opposed and aligned in preparation for joining the ends ltogether to form the bending ofthe end Vof the sheet to compensate for springback in the metal sheet after bending so that the bent end portions of the sheet will have the desired predetermined i curvature.

In operation of the tangent bending machine, the upper dies 8 and 9 are initially in the raised position and the corrugated sheet 1 is placed on the lower dies 6 and 7 with the flanges 3 of the sheet facing downwardly.

To position the leading edge of theV sheet 1 in proper alignment on the dies, an adjustable stoprrod 64, which is supported by a bracket 65 attached to die support plate 15, is disposed within one of the corrugations 56 of die 7. The end of sheet 1 engages the stop rod 64 and is thereby properly aligned, on the lower dies.

-The upper die 9 is then moved outwardly away from die 8 to the extended position byoperation of cylinder V374, and both dies v8 and 9.arethen lowered by action of cylinder 30 to clamp the sheet 1 between the upper and lowerl dies.v Y

n When in the clamped position, as shown in4 Fig. 9, the central portion of the sheet 1 bears against the flat surface completed shell. Y Y n After completion of the bending operations, the upper dies .-8 and 9 are raised, carrying'the bent sheet upwardly. The arm Z3 and die 9 are then moved inwardly by action of cylinder 34 to decrease the spacing between the dies 8 and 9 and thereby enablethe bent sheet to be slipped over the ends Vofthe arms 22 and 23. v The present invention provides an improved die'con' structionfor'a tangent bending machine which permits deeply corrugated sheet metal to be bent longitudinally of the corrugations to an extremely small radius of curvature. f

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I` claim: f Y l.Y A die vconstruction for a tangent bending machine employed to bend a corrugated metal sheet in a direc- I Vtion longitudinal of the corrugations, comprising a first adY corrugations in the inner portions of the lower dies per# mits lateral Vadjustment of the sheet ,inv these areas, and i thereby insures proper registry of the corrugations 2 of the rsheet with corrugations`54 andr56 of the lower die so that the corrugations 21 may conform with the corrugations 54 and 56 of the lower die. Y,

As the corrugations 2 are` generally not perfectly straight but have some degree of camber, it is ditlicult to have continuous perfect registryof the corrugations 2 and a die member of substantiallen'g'th. In a case such as this with imperfect registry, splits will frequently occur in the sheet during the bending operation. However, by eliminating the corrugations in the inner end portion of the dies 6 and 7, the corrugations 2 inthe area ofsurface 55 are able to adjust their kposition and thereby insure the proper registry of the corrugations 2 with the corrugations 54 of the lower dies regardless of camberaor` other warpage vof sheet 1.

With they sheet 1 clamped between the dies, one of the wardly around the curved working face of upper die 8 to Y progressively bendthe sheet 1 to the curvature ofthe face. progressivelyalong the radius of curvatureof the upper die to roll the metal sheet from the' linexof tangency.

After the first bend has been completed, VtheI die support plate 15 is pivoted downwardly and the opposite die support `plate 15 is then pivoted upwardly to progressively bend fthe sheet 1 around the curved working face of upperdie 9.

When the second bend has been completed, the respective die support plate is pivoted downwardly and the upper dies 8 and v9 are raised to release the partially bent sheet 1. The sheet is then removed from the'dies and reversed so that the opposite unbent end is inserted on the lower dies 6 and 7. vI'heupperdies are again lowered, clamping the sheet, and die 6 is again pivoted around upper die 8 to progressively bend the sheet to the radius of curvature of the ing end of the sheet to the curvature of the upper die.A

With this method of bending, pressure is applied Y Vdie-member vhaving a working face including a generally straight portion and a generally curved portion and havl ingfa series ofcorrugations 'extending substantially along the entire length ofv saidfrwerking face to lcomplement Y andreceive the corrugations of said sheet, and a cooperating second Ydie member supported for rocking movement with relation to said tirst'die member to progresi sively bend the sheet clamped between said membersjto 1 bersrtothe Ycurvaturefof'theworking face of the Yuppery the curvature of the working face Vof said rst die member, and said second die member having a working face including a generally flat'surface disposed in ccoperatlVY -ing relation with said straight portion of the workingface of`said`\first die member and a corrugated'surface disposed outwardly of said flat surface and in cooperatingfrelation with the curved portion of said working face of the first die member.

Y`2. A die construction for a tangent bending machine employed to bend a corrugated'metal'sheet 'in a direc'- tion longitudinal of the corrugations, comprising an upper die'meinber having a generally curved working face and a series of corrugations extending transversely' ofthef working face, and a cooperating lower die member'sup'- ported for rocking movement with vrelation to said upper die to progressively bend the sheetbetween'said mein-y die-"mer'n'bensaidA lower die member having a working Aface including a generally planar inner section disposedv at .the 'inner enrdfof said lower'die memberV and vhaving an outer 'section "formed -with a series of corrugations complementing the corrugations of theV working face of 'the upper die member, the outer end portion of said outer section being disposed at an inclined angle to the remaining portion of the outer section.

- 3.Y A die construction for a tangent bending machine employed to' bendY av corrugated metal sheet in a direction longitudinal of the corrugations, comprising a first die member having a working face including a central sectionand a .generally curved outer section, said rst die'fmember `having ajseries of corrugations kextending substantially along ,the entire length lof, s aid working face'tofcomplementandreceive the corrugationsfrof said sheet, and-a cooperating second die member supported Yfor rocking movement with relation to said rst die tion of the kworking face'of said first die member, said second die member having a working face including a generally dat surface disposed in cooperating relation with said'central section and an outer corrugated portionY disposed in cooperating relation with the curved section of the working face of said first die member, and means associated with the Working face of each of said die members for overbending the sheet beyond the desired radius of curvature to compensate for spring-back in the metal sheet.

4. A die construction for a tangent bending machine employed to bend a corrugated metal sheet in a direction longitudinal of the corrugations, comprising an upper die member having a Vgenerally curved working face and a series of corrugations extending transversely of the working face, a cooperating lower die member supported for rocking movement with relation to said upper die member to progressively bend the sheet between said members to the curvature of the working face of the upper die member, said lower die member having a working face formed with a series of corrugations complementary to the corrugations of said working face of the upper die member, and means associated with the inner portion of the working face of the lower die member for eiecting lateral adjustment of the metal sheet as the same is clamped between the die members and thereby eliminating tearing and splitting of the sheet during the` bending'operation.

5. A die construction Vfor a tangent bending machine employed to bend a corrugated metal sheetin a direction longitudinal of the corrugations with said corrugated metal sheet having a side ange extending along a side edge thereof, comprising an upper die member having a working face including a straight portion and a generally curvedV portion and having a series of corru gations extending transversely of the working face, and a cooperating lower die member supported for rocking movement with relation to said upper die to proigressively bend the sheet between said members to the curvature of the working face of the upper die member, said lower die member having a working face including a generally at surface disposed in cooperating relation with said straight portion of the working face of said upper die and having Ian outer portion disposed to cooperate with the curved portion of the working face of the upper die and formedrwith `a series of corrugations complementary to the corrugations of Vthe working face of the upper die member, and means associated with one of said die members for exerting a force against the edge of the ange of the sheet during the bending operation to prevent movement of the ange during the bending. Y Y f Y 6. A die construction for a tangent bending machine employed to bend a corrugated metal sheet ina direcv 'tion longitudinal of Ithe corrugations with said' corruber, said lower die member having a working face including a generally flat surface disposed lin Ycooperating relation with said straight portion of the working face of said upper die and having an outer portion disposed to cooperate with the curved portion of the working face ofthe upper die and formed with a series of corrugations complementing the Acorrugationsvof said working face of the upper die member and having a slot formed in the side edge portion thereof and disposed to receive the flange of saidsheet, said slot having a depth sufficient for the edge of the ange to bear against the bottom of said slot during the bending operation to thereby conne the flange during bending.

7. A die construction for tangent `bending ofcorrugated metal sheet in a direction longitudinal of the corrugations to form a generally oval-shaped article, comprising a frame, a pair of separate spaced first die members carried by the frame with each first die member having a generally curved working face and having a series of corrugations extending transversely of the working face, a pair of second die members supported by theframefor rocking movement with relation to the respect-ive rst'die members'to progressively bend the sheet to the curvature of the working face of the rst die members, said secondV die members having working faces provided with a series of corrugations complementing the corrugations of the working face of the respectivevrst die members, guide means associated with at least one of said rst die members Vfor maintaining alignment of the corrugations of the portion of the sheet projecting outwardly ofthe die members with the corrugations of the portion of the sheet disposed between the die members, and means for moving the first die members relative to each other to decrease the spacing therebetween after the bending operation and permit removal of the bent sheet from the first die members.

8. A die construction for a Vt-angent bending machine employed VVto bend a corrugated metal sheet in a direction longitudinal of the com1gations, comprising an upper die member havingv a generally curved working surface and a series of corrugations Vdisposed on the working surface, a cooperatinglower die member supported for rocking movement with relation .to the upper die to progressively bend the sheet between said die members to the curvature of the working face of the upper die member, said lower die member having a working face' formed with a series of corrugations complementary to the 'corrugations 'of said working face of the upper die member and having the outer portion of said working face disposed at an inclined angle with respect to the inner portion of said working face, means associated with the working face of the upper die member -to receive said inclined portion of the lower die member to eEect overbending of the end portion of the sheet to accommodate springback-of Vthe same,` and means associated with the inner portion lof the working face of theV lower die member for eecting lateral adjustment ofthe metal sheet as the `same is clamped between the die 'members and thereby eliminating tearing and splitting ofthe sheet during the bending operation.

References Cited in the file of this patent.

UNITED vSTATES PATENTS Y Moore Nov. 9,1954

FOREIGN PATENTS i 560,395 i vGreat Britain Apr.'3, `1944 

